Abstract

Quorum sensing (QS) is a bacterial communication mechanism that depends on population density. QS inhibitory activity of four bioactive agents and two essential oils was evaluated using the bacteria model Chromobacterium violaceum. On the other hand, antimicrobial activity was tested using two foodborne pathogens, Listeria monocytogenes and Escherichia coli. Agents were able to inhibit the violacein production, being tea tree and rosemary more effective than propolis and pollen, and resveratrol more effective than pomegranate. Tea tree and rosemary essential oils, applied at 0.5 μL/mL, reduced violacein production by more than 80%. In order to evaluate whether the inhibition of violacein production owed to the microbial growth reduction or acylated homoserine lactone inhibition, the antimicrobial activity was analyzed using C. violaceum as indicator. None of the tested agents showed antimicrobial activity at the minimal QS inhibitory concentration. Agents showed varying degrees of antibacterial activity against pathogens. Tea tree and rosemary resulted more effective than the others. These essential oils showed bacteriostatic effect on pathogen counts at low concentrations (0.5–1 μL/mL). When they were applied at concentrations higher than 2 μL/mL, bactericidal effect was observed against E. coli and L. monocytogenes. These findings strongly suggest that these agents have potential to be good preservatives because of anti-QS capacity and antimicrobial properties.

Practical Applications

Food spoilage is a complex process, and excessive amounts of foods are lost due to microbial spoilage even with modern day preservation techniques. Another problem related to public health is the contamination of foods with human pathogen microorganisms. Quorum sensing (QS) is a cell-to-cell communication mechanism by which bacterial population measures its cell density. Because many important animal and plant pathogens use QS to regulate virulence, the interruption of bacteria QS have broad applicability for biological control of disease-causing organisms. It is considered a good strategy to reduce or prevent spoilage reaction in foods. In this work, we investigated antimicrobial activity against foodborne pathogens and anti-QS activity (using Chromobacterium violaceum) of some bioactive extracts and essential oils. The results obtained from this study indicate that agents tested could potentially be used as natural preservatives to prolong shelf life and ensure safety of foods.